The present invention relates to gauges used in industry for measuring or checking the depth of a hole which may be an internally threaded or tapped hole.
Testing threaded holes is usually carried out in two successive operations: a first operation for checking the diameter and the quality is effected by screwing into the tapped hole one or more standard gauges comprising a threaded head, a central narrowed portion and a handling sleeve. A second operation for checking the depth is achieved by screwing into the hole a length gauge, comprising for example a threaded head, a handling sleeve and a shoulder intended to come into abutment against the edges of the hole at the end of screwing. The high cost of standard gauges leads to using the same standard gauge for checking all the tapppings having the same characteristics but of any depth, and in using a different length gauge for each tapping depth. However, the wear of a length gauge, following numerous tests, cannot be compensated for and ends in this gauge being discarded, which is moreover relatively expensive because of its unitary construction.
Gauges comprising certain improvements have been proposed; thus the review Technical Digest--Western Electric describes a gauge comprising a body having a probe intended to penetrate into the hole, a mobile part sliding freely over the body and whose front end comes into abutment against the outer part of the workpiece to be checked; stops limit the sliding of the mobile part and prevent rotation thereof with respect to the body. This device has the disadvantage of being specialized for a single hole size, and for each diameter and/or depth an adequate gauge is required. The length of the probe and its position with respect to the body are not adjustable, the probe not being interchangeable either. The mobile part forms the handling member and is necessarily rotated, which prevents this type of gauge from being used in some applications.
The review IBM TECHNICAL DISCLOSURE BULLETIN describes a similar gauge in which a probe is inserted by screwing along a central axis of a body forming a handling member. No means is provided for allowing axial adjustment of the probe on the body. A mobile part slides and rotates freely on the body and comes into abutment against the workpiece to be checked. The user must deliberately hold the mobile part against the workpiece to be tested. Furthermore, the device does not allow commercially available standard gauges to be used, since the probes must be formed specially for fitting them to the body.
U.S. Pat. No. 4,314,406 describes a device allowing measurement by transfer to a subsidiary apparatus, which considerably complicates the operations.
Patents DE No. 1 698 339 and U.S. Pat. No. 2,517,846 describe micrometric depth gauges whose function is to measure the depth of a hole and cannot measure a tapping depth. In fact, a mobile part, carrying the workpiece to be tested, moves with respect to the body exclusively by screwing; the pitch of this screwing is practically always incompatible with the pitch of the tapping to be checked.
The present invention has more especially as object to obviate the disadvantages of known devices by making available to the user a general purpose gauge, allowing ready adjustment of the effective gauge length to adapt it to the nominal length of the hole or tapping to be checked, either because this adjustment is made necessary through the wear resulting from intensive use, or because said length is modified because, for example, of a change in tolerance during manufacture or because it is desired to test holes having different nominal lengths.
According to one object of the invention, the device allows insertable commercially available probes to be used, and for example standard plug gauges used for checking the diameter and the quality of tappings formed. Thus, the device allows, by a single operation on the part of the user, the quality and the diameter of the tapping to be checked and its length measured simultaneously whereas known devices require two successive separate operations, a first one for the diameter and a second one for the length.
According to another object of the invention, the device allows threaded plugs or probes to be fitted to the gauge whose sleeves have very different diameters and shapes, allowing more especially holes or tappings of very different dimensions to be checked.
According to another object of the invention, the device allows holes to be checked formed in parts of different shapes, by being more especially adjustable to reference surfaces of different shapes. With the device of the present invention, holes may for example be checked disposed at the bottom of a groove by taking as reference surface the bottom of the groove. It may also be adapted to surfaces of different shapes such as cones. spherical surfaces or others.
According to another object of the invention, the gauge may serve for tests other than those of the effective tapped depth, such as testing blind bores, and recessed bearing surfaces.
According to another object of the invention, a tool is provided of low cost price, permitting however a remarkably reliable and accurate multi-purpose test.